Liquid crystal displays (LCDs) and organic light-emitting diode (OLED) display devices have been widely used in our daily lives, and resolution, gamut and brightness of the display devices are increasingly demanded. Recently, such products with 500 pixel per inch (PPI), and even 600 PPI have been developed.
For a conventional LCD, an array substrate and a color filter substrate are arranged opposite to each other to form a cell, and during the cell formation, patterns on the array substrate may be offset from the corresponding patterns on the color filter substrate. This offset may result in a decrease in an aperture ratio as well as light leakage. In addition, the larger the PPI of the LCD, the smaller the aperture ratio, the smaller the brightness and the gamut, and the higher the power consumption.
In order to eliminate the offset between the array substrate and the color filter substrate, increase the aperture ratio and reduce the production cost, such a technology where a color filter and a black matrix are arranged on the array substrate, i.e., Color Filter On Array (COA), has been developed. To be specific, the black matrix is arranged on a data line, a gate line and a thin film transistor (TFT) of the array substrate, so as to reduce the offset between the patterns on the array substrate and the corresponding patterns on the color filter substrate during the cell formation, thereby to increase the aperture ratio, reduce the production cost and improve the image quality.
However, when the black matrix is made of a metal material, light may be reflected by the black matrix. As a result, a contrast will be degraded and the image quality will be adversely affected.